This invention generally relates to an improved toolholder assembly and method, and is specifically concerned with an improved toolholder assembly comprising a nozzle assembly for advantageously redirecting the coolant stream to optimize lubrication, heat removal and chip removal when deep cuts are made in a relatively rotating workpiece.
Toolholder assemblies having an opening for directing a liquid coolant stream at a cutting interface are known in the prior art. Such toolholder assemblies generally comprise a toolholder body having a clamping arrangement on one side for detachably mounting any one of a number of cutting inserts, a shank on its other side for detachably mounting the toolholder assembly to a machining mechanism that moves the toolholder with respect to a rotating workpiece in order to groove, thread, or cut off the same, and a coolant opening on the side of the toolholder body that faces the insert-holding clamp for directing a stream of liquid coolant at the interface between the cutting edge of the insert and the workpiece. The liquid coolant used is typically a water soluble-oil which advantageously serves to lubricate the interface between the cutting edge of the insert and the workpiece, as well as to remove heat and metal chips which would accelerate the wear of the cutting insert and interfere with and degrade the quality of the cut. The coolant-directing opening in the toolholder body is typically connected to a source of pressurized coolant through a coolant bore or passageway which extends all the way through the toolholder body and the shank which connects it to the machining mechanism.
In such conventional toolholder assemblies, the coolant opening directs the stream of coolant at an angle having directional components which are both orthogonal to and parallel with the axis of rotation of the workpiece, which in turn causes the stream of coolant to impinge on the interface between the cutting insert and the workpiece at an angle which is oblique with respect to the workpiece axis of rotation. The applicant has observed that, while such an oblique coolant stream adequately lubricates, cools and removes the metal chips when relatively shallow cuts are made on the workpiece, such an oblique-angled coolant stream becomes progressively less effective the deeper that the cutting insert cuts into the workpiece as the shoulders of metal on either side of the cut tend to interfere with the direct impingement of the coolant stream on the cutting interface. While some if not most of the coolant might succeed in flowing over the interfering shoulder in the workpiece and trickle down into the cutting interface, such a trickling flow of coolant is decidedly less effective in providing the lubricating, heat removing and chip removing functions that a directly impinging stream of coolant performs. Hence, the quality of the resulting cut in the workpiece may be seriously impaired, and wear on the cutting insert is increased.
Clearly, what is needed is a means for modifying a conventional toolholder assembly to redirect the stream of coolant from the coolant opening in the toolholder body so that it is capable of directly impinging the interface between the cutting insert and the workpiece regardless of the depth of the cut. Ideally, such a modification mechanism should be capable of adjusting the angle of the coolant stream not only in a plane orthogonal with respect to the axis of rotation of the workpiece, but linearly along this axis as well so as to be able to project a directly impinging stream of coolant into the interface for a variety of cutting inserts having a variety of different shapes. Finally, it would be desirable if the modification mechanism were simple in construction, and capable of being retrofitted onto the body of a prior art toolholder assembly with a minimum amount of machining effort and with a minimum amount of interference with the working profile of the toolholder assembly so that the maneuverability of the assembly is not significantly impaired.